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#1020 by rfmwguy on 26 Sep, 2016 17:58
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I'm not sure Cannae's pillbox cavity should be considered as different from the Emdrive. Even if the shape is different, the mechanics seem to be very similar: asymmetric resonant microwave cavities. It would add some unnecessary overhead to have to track the Cannae drive updates in some other topic IMO.
Yes, as long as a theory can pertain to EmDrive design build or test, its helpful, especially when the theory has practical engineering aspects, meaning there is a way to test the theory with an experiment/hardware. Alcubierre may never fit this criteria unfortunately.
I agree with you and with Dr. Rodal that discussion around/pertaining to piezoelectric/electrostictive stack devices belongs to Woodward effect's own topic.
But any theoretical discussion trying to explain the Emdrive as described above (asymmetric resonant microwave cavities) I do think it belongs here.
Best I can tell Cannae is using symmetrical endplates, although they've used slotting rings internally on one of the "plates" and the frequencies are not microwave, but I haven't followed it recently. Last contact I had with Guido was to seek permission to visit during a test this summer and was politely turned down.
p.s. I think we owe a great deal to Paul at EW who's last day before retirement might have just passed. Without him, I am thoroughly convinced we would not be as far along with this concept. Hope he gets a chance to post again here and elsewhere. Hand's on practitioners are hard to come by
Happy "retirement" Paul!
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#1021 by Bob012345 on 26 Sep, 2016 18:08
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The statement "Since the 10 years of operation of the 200Kwe generator gives only 6.311*10^13 Joules" is in the ships frame or really, frames. If you claim it's also in the observer frame you are ignoring the multiplicative factor that converts between frames.
It is in the ship frame. I did not made the calculus of how much time was elapsed in the Earth frame. Anyway it will not change the magnitude of the problem : around 10^7. More than 10 years will have occured on earth, but not 100 million years.
If the over unity compliant is correct, Shawyer's probe should run into that condition in under 7 seconds from launch. The Cannae Probe would end at 267 seconds. So, easy to tell. -
#1022 by rfmwguy on 26 Sep, 2016 18:12
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Thanks. Builders have had a few conversations about what a flight unit should be made of. One of our concerns was thermal coefficients as you point out. Whatever melts, deforms, delaminates or otherwise misbehaves in temperature extremes is a problem. Base metal is the safest bet; composites ramp up potential problems, but are ideal for experimentation (prototypes/engineering models/proof of concept hardware) down here on earth imo. I chose to stick with a heaver base metal even though it oxidizes. There is no coating that might degrade Q, heat up and possibly vaporize/reflow/morph into a face-eating bacteria (that's a joke). Builders have no authoritarian blueprints so are free to try their own thing within the general guidelines that Shawyer started with years ago.If I understand you correctly, you would not need to start with a printed master. A lost wax master near enough the final dimensions needed could be fabricated from clay or ceramics at far less expense, then milled to the desired finished net-shape. Casting the copper to a close approximation before milling would save $$, compared to starting with a solid block. And if the end product were to be plated with a greater than skin depth silver, the purity of the cast copper may not even be as much of an issue.
If I had an educated guess, the cheapest option would be to 3dprint directly in ceramic powder using a binder. Its surface needs then to be smooth using a filler, cured, then glazed and cured again.
I have not tried it myself, but glazed ceramics can be copper plated...You'll then have a smooth surface without the need of machining.
And please, to all DIY's out there...Don't use the popular ceramic-PLA filaments as they contain way too much PLA and could melt at low temperatures. Same applies for those copper/bronze, etc filaments.. -
#1023 by Flyby on 26 Sep, 2016 18:36
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With that warning, I was actually not referring to you, Shell or Mono. As engineers, you all know your stuff, that's obvious.
But when the EagleWorks review hits the street, I fear a lot more hobbyists with 3Dprinting dreams will have a go at building their own version of the EMdrive. Hence the warning .... maybe I should have said "to all future DIY's..."
It certainly was not the intention of belittling any of the current DIY builders.
My apology if it was perceived in such way... -
#1024 by tchernik on 26 Sep, 2016 18:56
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Yes, that would be a more clear and logical split of the thread . It was first proposed on thread 2 or 3, but the consensus at that time was to keep experimental and theoretical discussions in the same thread. If I recall correctly the consensus was that keeping both experimental and theoretical discussions together would foster synergy, and lead to better experiments.
And conversely, better experiments, as, for example the experiments from SeeShells and Monomorphic, would lead to better examination of theoretical explanations.
SeeShells and Monomorphic, who, instead of following a single theoretical course, are pursuing different explanations in parallel: with and without polymer inserts. SeeShells also exploring interferometry changes (with her central quartz rod). Monomorphic pursuing different shapes (conical and flat sides). SeeShells pursuing numerical calculations with Meep, with Aero. Monomorphic using FEKO for calculations. SeeShells pursuing all avenues "the kitchen sink"
Looking back, we must admit that there has been great synergy in the past threads !
Besides dividing the topic would result in duplication, because everything is so new and changing that the theoretical topic would cite and include the practical results verbatim, as soon as they are released, and the experimental topic would cite the theoretical cogitations for understanding the results seen, resulting in each topic kind of mirroring each other anyway.
What I see as potential points where things must split up, is when there are missions and for-sale devices exploiting these effects for practical purposes (if that ever happens). In an analogous way to how there are separate topics for the different missions to space and the different kinds of launchers that we can see in this same forum. -
#1025 by Gilbertdrive on 26 Sep, 2016 19:24
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What I am trying to say is that the folks that say there is an energy violation are comparing energy in different frames.
I still fail to see what is wrong with comparing energy in different inertial frames, as long as you're being careful. Of course kinetic energy is different in different frames, but the total energy must be conserved no matter what intertial frame you choose. It's easy to show that while the kinetic energy of a "constantly accelerating device" grows faster and faster in a "rest" frame as the device speeds up, this gets offset by other factors (kinetic energy of the propellant in the case of a conventional rocket, etc), so that the total energy spent over a unit of time is exactly the same, regardless of the reference frame.
It's not wrong to compare but to equate. Some are saying power expended x time in the ships frame must equal or exceed the total kinetic energy in the earth observer frame where the ship starts from rest. And if the velocity exceeds a critical number, the acceleration just falls off to conserve energy. I used to think that but now I don't. What magic mechanism alerts the ship that it's crossed that number wrt earth frame and decreases the acceleration?
Consider a hypothetical rocket that can do 10000 burns at a delta v of 1000 m/s. Each burn requires a total energy of E, maybe only 1% goes to the ship. After the first burn, the kinetic energy of the ship wrt earth is 5E5/kg so assume the burn released 5E7 J/kg in its frame. What's the total energy released in the ships frame after 10000 burns? It should be 5E10J/kg. What's the kinetic energy wrt earth? It should be 5E13J/kg. No doubt some will claim nature conspires to prevent this by making the mass requirements great enough so it's never practical to make such a rocket. That's saying an EMDrive like device should never work at all. But if it works at all, there is no feasible mechanism I am aware of to decrease acceleration for a fixed force at a fixed power.
Consider that rocket doing the first burn seen from two frames, earth and another frame moving at 0.5c in the opposite direction. From earth, the first burn gives the ship a kinetic energy of 5E5J/kg. From the other frame the kinetic energy gain of the ship is huge from that burn 1.5E11J/kg. But counting the exhaust, it's the same energy released by the ship. There are frames where the energy balance is negative and energy burn is more than kinetic energy in that frame and there are frames where energy burn is less than the ships kinetic energy in that frame. All frames agree how much energy the ship burned as actual fuel. In all frames one can use the work energy theorem and get a prefect balance between force, distance and energy. According to some, the acceleration form the burns deceases to preserve CoE in some frames, but not others. This is chaos.
Can you tell who on this forum claimed that the acceleration from the burns was decreasing in some frames but no others ? I am afraid there were misunderstanding. -
#1026 by WarpTech on 26 Sep, 2016 19:25
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A two piece construction is also possible. This also saves a little off the 3d printing cost if the seam is in the middle.
Mono,
Middle seam: ASA: $620, ABS: $500
Big End seam: ASA: $825, ABS: $660
there are some issues with ABS 3dprinting as ABS tends to warp a lot. (I own a small 3dprinting shop).
Personally, I have not used ASA yet, but from reports I'm reading it has a superior warping resistance and seems to handle extreme conditions better.
Just make sure it doesn't cool off to rapidly or you'll get "splitting"...
https://3dprintingindustry.com/news/testing-asa-3d-printing-filament-weather-resistant-alternative-abs-62785/
Acrylonitrile butadiene styrene (ABS) is a common thermoplastic polymer with very low glass transition temperature (approximately 105 °C (221 °F)).
In general, making the EM Drive walls with a thermoplastic polymer will present other problems, besides warping.
We all know about the thermal effects in the EM Drive by now. The thermal conductivity and the thermal diffusivity of these polymers is several orders of magnitude lower than that of copper. So even if you have an internal thin layer of copper or silver, the thermoplastic polymer will act as an insulator. It is better to have a solid wall of a material (like copper or silver) with high thermal conductivity and high thermal diffusivity.
The warping is a consequence of the low modulus of Elasticity of unreinforced thermoplastic polymers as compared to metals like copper and silver. NASA Eagleworks used FRP wich is a composite where glass-fibers reinforces a thermoset epoxy to provide a higher modulus of elasticity.
I'm also getting a quote for CNC milling. We will see what that comes to as it seems like the parts would need to be milled from large solid blocks of copper - which is extremely expensive - thousands of dollars each.
If I use ASA and print 1cm thick walls and then electroplate a thick copper coat of 3mm after etching, then polish down to 2mm, it should be rigid enough. Though I think the process of etching the ASA, and electroplating 3mm of copper would be a difficult undertaking as a DIY.
Another option using 3D printed plastic is to use the plastic as a 'lost wax' master and cast copper into a near-net-shape which can then be cut down and polished by a CNC milling process. Would save $$$ on machining time and up-front material cost.
If I understand you correctly, you would not need to start with a printed master. A lost wax master near enough the final dimensions needed could be fabricated from clay or ceramics at far less expense, then milled to the desired finished net-shape. Casting the copper to a close approximation before milling would save $$, compared to starting with a solid block. And if the end product were to be plated with a greater than skin depth silver, the purity of the cast copper may not even be as much of an issue.
For Monomorphic, I would suggest splitting the frustum down the middle "vertically" instead of horizontally and eliminate the end plates all together. Then create a 1/2 frustum mould for casting. You can then cast each half, everything is open and easy to mill and polish, and then bolt them together. It could then be cast in copper, brass, nickel, silver plated, whatever you want and they would all be nearly identical. "Mass production scheme!"
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#1027 by Gilbertdrive on 26 Sep, 2016 19:36
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Gilbertdrive writes;
QuoteBut, as Shawyer calculates the imput power of the emdrive, he founds an enormous 6,04*10^20 Joules, he is happy and he considers that CoE is verified.
That is where the important point here. Shawyer admit that the Kinetic Energy in the Earth referential can not be superior to the energy spent by the ship. He just forgot to take into account his own theory in his thrust formula, and than, he made a mistake in calculating the imput power. (I calculated 6.311*10^13 Joules for 10 years of operation of the 200KwE generator, not taking into account the fact that the time goes more slowly for the ship.
No, I don't think he forgot anything. If he did then the reviewers did too which is unlikely. Shawyer's reduction in thrust as I understand it, is due to the cavity not supporting the acceleration, not actual speeds but regardless, his energy calculation for his probe allows continuous acceleration reduced by relativistic effects.
It is an authority argument. "If it is published, there is no big mistake"
At least, you should concede that the reviewer who accepted the Kinetic Energy to be calculated by 1/2*mv² for a speed of 0,67C made here a mistake, since the relativist formula was needed. The aim was to calculate a ratio that is around 0,31. so the relativist formula was making a real difference.
Also, the main point of my intervention was to show that in Shawyer theory paper, the thrust is supposed to decrease as acceleration from the time frame of the departure of the ship was increasing, so that CoE is verified. Are you convinced by the extracts that I have given, or do you think that, is this paper theory, the force is supposed to be constant ?
Here, the question is not what is true, it is what Shawyer is saying. Once we will agree on what Shawyer is saying in his theory paper, we can go to the other debate. -
#1028 by EnlightenMe on 26 Sep, 2016 19:46
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I've been working on spherical end-plate emdrive meshes that can be 3d printed or CNC machined. Not a lot of 3d printing shops can print something the size of the side walls in a ~2.4Ghz TE013 frustum, so for one option, I have split the side walls in two.
I can print the entire 3-piece frustum in ASA for $670. And then copper/silver electroplate the ASA. I still need to add bolt holes, but haven't decided on a bolt size yet.
Monomorphic,
Instead of pursuing 3d printed or CNC milled spherical endplates, have you considered creating the endplates yourself, using a method similar to this?
http://www.bbastrodesigns.com/JoyOfMirrorMaking/Intro.html
If a pitch lap was good enough for Newton to create the spherical mirror for his reflecting telescope, it might serve you well, too. :-) -
#1029 by rq3 on 26 Sep, 2016 21:43
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A two piece construction is also possible. This also saves a little off the 3d printing cost if the seam is in the middle.
Mono,
Middle seam: ASA: $620, ABS: $500
Big End seam: ASA: $825, ABS: $660
there are some issues with ABS 3dprinting as ABS tends to warp a lot. (I own a small 3dprinting shop).
Personally, I have not used ASA yet, but from reports I'm reading it has a superior warping resistance and seems to handle extreme conditions better.
Just make sure it doesn't cool off to rapidly or you'll get "splitting"...
https://3dprintingindustry.com/news/testing-asa-3d-printing-filament-weather-resistant-alternative-abs-62785/
Acrylonitrile butadiene styrene (ABS) is a common thermoplastic polymer with very low glass transition temperature (approximately 105 °C (221 °F)).
In general, making the EM Drive walls with a thermoplastic polymer will present other problems, besides warping.
We all know about the thermal effects in the EM Drive by now. The thermal conductivity and the thermal diffusivity of these polymers is several orders of magnitude lower than that of copper. So even if you have an internal thin layer of copper or silver, the thermoplastic polymer will act as an insulator. It is better to have a solid wall of a material (like copper or silver) with high thermal conductivity and high thermal diffusivity.
The warping is a consequence of the low modulus of Elasticity of unreinforced thermoplastic polymers as compared to metals like copper and silver. NASA Eagleworks used FRP wich is a composite where glass-fibers reinforces a thermoset epoxy to provide a higher modulus of elasticity.
I'm also getting a quote for CNC milling. We will see what that comes to as it seems like the parts would need to be milled from large solid blocks of copper - which is extremely expensive - thousands of dollars each.
If I use ASA and print 1cm thick walls and then electroplate a thick copper coat of 3mm after etching, then polish down to 2mm, it should be rigid enough. Though I think the process of etching the ASA, and electroplating 3mm of copper would be a difficult undertaking as a DIY.
This has been discussed before. Indeed, quite a while ago I suggested that the ideal cavity would be constructed the way that most precision waveguides are constructed. A master is made out of machinable wax. The wax master is electroplated with just about anything you care to use. The wax is removed by solvent or melting.
The resulting object has an interior surface finish effectively equal to the surface finish of the wax master. These days, that finish can be on the order of nanometers. If you'd like your frustum to be very conductive yet well protected from oxidation, the wax master would first get a gold flash, followed by silver for conductivity, followed by copper for mechanical strength.
This is a common industrial process. While you're at it, an earlier post of mine suggested making the skin effect impedance of the frustum equal to the injection impedance. The walls would be plated with a relatively high resistance alloy like nichrome. If the skin effect impedance matched the injection impedance ("free space"), then the walls would be effectively invisible, from the microwave field perspective. Perhaps this is why Shawyer's flying cars haven't materialized with superconductive frustums.
A matched wall impedance would lower the Q, but would do to evanescent waves....? I suspect Q is less important than evanescent wave transport THROUGH the walls. With a very high Q, and extreme impedance mismatch, there is NO wall transport. With match, who knows? No one has ever tried, except perhaps, by accident, with the Emdrive. To date, microwave engineering has either been trying to keep all of the energy inside (wavequide), or all the energy transmitted (antenna). -
#1030 by rq3 on 26 Sep, 2016 21:49
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A two piece construction is also possible. This also saves a little off the 3d printing cost if the seam is in the middle.
Mono,
Middle seam: ASA: $620, ABS: $500
Big End seam: ASA: $825, ABS: $660
there are some issues with ABS 3dprinting as ABS tends to warp a lot. (I own a small 3dprinting shop).
Personally, I have not used ASA yet, but from reports I'm reading it has a superior warping resistance and seems to handle extreme conditions better.
Just make sure it doesn't cool off to rapidly or you'll get "splitting"...
https://3dprintingindustry.com/news/testing-asa-3d-printing-filament-weather-resistant-alternative-abs-62785/
Acrylonitrile butadiene styrene (ABS) is a common thermoplastic polymer with very low glass transition temperature (approximately 105 °C (221 °F)).
In general, making the EM Drive walls with a thermoplastic polymer will present other problems, besides warping.
We all know about the thermal effects in the EM Drive by now. The thermal conductivity and the thermal diffusivity of these polymers is several orders of magnitude lower than that of copper. So even if you have an internal thin layer of copper or silver, the thermoplastic polymer will act as an insulator. It is better to have a solid wall of a material (like copper or silver) with high thermal conductivity and high thermal diffusivity.
The warping is a consequence of the low modulus of Elasticity of unreinforced thermoplastic polymers as compared to metals like copper and silver. NASA Eagleworks used FRP wich is a composite where glass-fibers reinforces a thermoset epoxy to provide a higher modulus of elasticity.
I'm also getting a quote for CNC milling. We will see what that comes to as it seems like the parts would need to be milled from large solid blocks of copper - which is extremely expensive - thousands of dollars each.
If I use ASA and print 1cm thick walls and then electroplate a thick copper coat of 3mm after etching, then polish down to 2mm, it should be rigid enough. Though I think the process of etching the ASA, and electroplating 3mm of copper would be a difficult undertaking as a DIY.
Or they could be machined from large solid blocks of almost anything. Almost anything can be coated with almost anything. Copper on baby shoes, nickel on wood, gold on plastic, plutonium on niobium...there are companies that do this stuff all the time. Just saying. -
#1031 by Kenjee on 26 Sep, 2016 23:20
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A two piece construction is also possible. This also saves a little off the 3d printing cost if the seam is in the middle.
Mono,
Middle seam: ASA: $620, ABS: $500
Big End seam: ASA: $825, ABS: $660
there are some issues with ABS 3dprinting as ABS tends to warp a lot. (I own a small 3dprinting shop).
Personally, I have not used ASA yet, but from reports I'm reading it has a superior warping resistance and seems to handle extreme conditions better.
Just make sure it doesn't cool off to rapidly or you'll get "splitting"...
https://3dprintingindustry.com/news/testing-asa-3d-printing-filament-weather-resistant-alternative-abs-62785/
Acrylonitrile butadiene styrene (ABS) is a common thermoplastic polymer with very low glass transition temperature (approximately 105 °C (221 °F)).
In general, making the EM Drive walls with a thermoplastic polymer will present other problems, besides warping.
We all know about the thermal effects in the EM Drive by now. The thermal conductivity and the thermal diffusivity of these polymers is several orders of magnitude lower than that of copper. So even if you have an internal thin layer of copper or silver, the thermoplastic polymer will act as an insulator. It is better to have a solid wall of a material (like copper or silver) with high thermal conductivity and high thermal diffusivity.
The warping is a consequence of the low modulus of Elasticity of unreinforced thermoplastic polymers as compared to metals like copper and silver. NASA Eagleworks used FRP wich is a composite where glass-fibers reinforces a thermoset epoxy to provide a higher modulus of elasticity.
I'm also getting a quote for CNC milling. We will see what that comes to as it seems like the parts would need to be milled from large solid blocks of copper - which is extremely expensive - thousands of dollars each.
If I use ASA and print 1cm thick walls and then electroplate a thick copper coat of 3mm after etching, then polish down to 2mm, it should be rigid enough. Though I think the process of etching the ASA, and electroplating 3mm of copper would be a difficult undertaking as a DIY.
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#1032 by rfmwguy on 26 Sep, 2016 23:28
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With that warning, I was actually not referring to you, Shell or Mono. As engineers, you all know your stuff, that's obvious.
Didn't think that at all. At one time I thought NSF would be a great place for DIY tips, techniques but decided to back off of that philosophy. However, your inputs are still in that spirit and am glad to see it.
But when the EagleWorks review hits the street, I fear a lot more hobbyists with 3Dprinting dreams will have a go at building their own version of the EMdrive. Hence the warning .... maybe I should have said "to all future DIY's..."
It certainly was not the intention of belittling any of the current DIY builders.
My apology if it was perceived in such way...
My guess is the world will soon see a rash of prospective EmDrive builders. Guidance, especially towards safety is needed. Active posters can pick up that banner if they wish. Back to inactive for me...I've had my fill for a while - Cheers, Dave -
#1033 by oyzw on 27 Sep, 2016 00:35
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I have used the spinning process manufacturing cavityA two piece construction is also possible. This also saves a little off the 3d printing cost if the seam is in the middle.
Mono,
Middle seam: ASA: $620, ABS: $500
Big End seam: ASA: $825, ABS: $660
there are some issues with ABS 3dprinting as ABS tends to warp a lot. (I own a small 3dprinting shop).
Personally, I have not used ASA yet, but from reports I'm reading it has a superior warping resistance and seems to handle extreme conditions better.
Just make sure it doesn't cool off to rapidly or you'll get "splitting"...
https://3dprintingindustry.com/news/testing-asa-3d-printing-filament-weather-resistant-alternative-abs-62785/
Acrylonitrile butadiene styrene (ABS) is a common thermoplastic polymer with very low glass transition temperature (approximately 105 °C (221 °F)).
In general, making the EM Drive walls with a thermoplastic polymer will present other problems, besides warping.
We all know about the thermal effects in the EM Drive by now. The thermal conductivity and the thermal diffusivity of these polymers is several orders of magnitude lower than that of copper. So even if you have an internal thin layer of copper or silver, the thermoplastic polymer will act as an insulator. It is better to have a solid wall of a material (like copper or silver) with high thermal conductivity and high thermal diffusivity.
The warping is a consequence of the low modulus of Elasticity of unreinforced thermoplastic polymers as compared to metals like copper and silver. NASA Eagleworks used FRP wich is a composite where glass-fibers reinforces a thermoset epoxy to provide a higher modulus of elasticity.
I'm also getting a quote for CNC milling. We will see what that comes to as it seems like the parts would need to be milled from large solid blocks of copper - which is extremely expensive - thousands of dollars each.
If I use ASA and print 1cm thick walls and then electroplate a thick copper coat of 3mm after etching, then polish down to 2mm, it should be rigid enough. Though I think the process of etching the ASA, and electroplating 3mm of copper would be a difficult undertaking as a DIY.
https://www.youtube.com/watch?v=0RY0cjSUPGg?t=46 -
#1034 by Tellmeagain on 27 Sep, 2016 03:08
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No, you don't get massive 'free' energy. What you get is different energies in different reference frames. You can see that simply by the following example. Say a ship is moving wrt earth frame at just under 0.5c by 1000m/s and you observe it. The ship makes a burn to increase its velocity wrt you by 1000m/s to exactly 0.5c wrt you. For a 10,000kg ship, how much energy does the pilot need to add? It depends on which reference frame. In the ships frame the pilot only needs to do the same burn to gain 1000m/s as always which is 5E9 J. You would say its about 1.5E15 J. It does gain that but not by the ship expending that energy in its reference frame. It would be the same regardless of a rocket of an EmDrive engine except the EmDrive would be more efficient. No doubt some will claim the rocket fuel already has kinetic energy, which it does, but that's natures gift, not something the ship had to provide by internal energy release stored as fuel because it never had that energy content to begin with. If someone objects further then consider that the ship was launched from a planet already moving at just under 05c to start with.
The bottom line is that the actual energy to get to the stars is probably a lot less that convention dictates.
P.S. I understand Woodward and allies previously released an essay demolishing the free energy or over unity arguments.
http://ssi.org/epi/Over-Unity_Argument_&_Mach_Effect_Thrusters.pdf
Was that discussed at the workshop?
Correct.
In the ship's frame, the only one which matters, the energy needed to alter velocity in relation to some desired destination is always the same as the ship's mass does not alter. Well not so much as it matters.
BTW Jim Woodward makes a good comment:
http://ssi.org/epi/Over-Unity_Argument_&_Mach_Effect_Thrusters.pdfQuoteWe routinely hear a criticism of METs based upon an argument that claims: if a
MET is operated at constant power input for a sufficiently long time, it will acquire
enough kinetic energy to exceed the total input energy of operation. Assuming this
argument to be correct, critcs assert that METs violate energy conservation as the ratio of
the acquired kinetic energy to total input energy exceeds “unity.”
Contrary to this “over-unity” assumption, this argument is based on flawed
physics and, consequently, wrong. The fact that the argument applies to all simple
mechanical systems (in addition to METs) should have alerted critics to their mistake.
But it didn’t.
So, a dumb idea that should have been quickly buried is still with us. The
purpose of this essay is to carry out a long overdue burial.
Interesting paper. I glanced at it and found the math was within my ability. So I printed it out to take a closer look. I think I will be able to find something wrong in his argument. But I may not be able to. Whatever the result is, I will write a swift report about my findings.
As promised, I wrote a short report. The attached picture is a screen short of the first page of the report. The whole report is also attached to this email. As meberbs, I now think Professor Woodward does not have credit in his theory.
Edit: Updated report because originally on page 3 I used M for both mass and for mega (10^6), thus may cause confusion. I updated the report so that now M is only for mass.
Update: I updated the Woodward.pdf to Woodward_updated.pdf (below the screenshot); Updated the section about the rocket equation (added discussion of relative speed of the propellant). Now it is related to rocket equation we saw elsewhere.
Update2: Added Woodward_updated2.pdf analysis of the rocket energy for the rocket equation at the end of section III. Link is at the end of this post.
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#1035 by WarpTech on 27 Sep, 2016 03:35
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I have used the spinning process manufacturing cavity
I'm also getting a quote for CNC milling. We will see what that comes to as it seems like the parts would need to be milled from large solid blocks of copper - which is extremely expensive - thousands of dollars each.
If I use ASA and print 1cm thick walls and then electroplate a thick copper coat of 3mm after etching, then polish down to 2mm, it should be rigid enough. Though I think the process of etching the ASA, and electroplating 3mm of copper would be a difficult undertaking as a DIY.
Idea: Here's a cheap and sandy way to DIY and make spherical end plates. Green sand casting. http://foundry101.com/index.htm
You can use the 3d printed plastic part to create a template to impress into the sand. Then do a pour and polish. A precision finish would be faster by CNC. You could cast the sphere convex or concave, for each end cap. You may even find a foundry to cast these cheap for you, using your 3d printed template to save time.
I think a better finish can be had if you use finer grained sand, or even clay. It's not expensive like making a mould for casting.
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#1036 by WarpTech on 27 Sep, 2016 03:43
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No, you don't get massive 'free' energy. What you get is different energies in different reference frames. You can see that simply by the following example. Say a ship is moving wrt earth frame at just under 0.5c by 1000m/s and you observe it. The ship makes a burn to increase its velocity wrt you by 1000m/s to exactly 0.5c wrt you. For a 10,000kg ship, how much energy does the pilot need to add? It depends on which reference frame. In the ships frame the pilot only needs to do the same burn to gain 1000m/s as always which is 5E9 J. You would say its about 1.5E15 J. It does gain that but not by the ship expending that energy in its reference frame. It would be the same regardless of a rocket of an EmDrive engine except the EmDrive would be more efficient. No doubt some will claim the rocket fuel already has kinetic energy, which it does, but that's natures gift, not something the ship had to provide by internal energy release stored as fuel because it never had that energy content to begin with. If someone objects further then consider that the ship was launched from a planet already moving at just under 05c to start with.
The bottom line is that the actual energy to get to the stars is probably a lot less that convention dictates.
P.S. I understand Woodward and allies previously released an essay demolishing the free energy or over unity arguments.
http://ssi.org/epi/Over-Unity_Argument_&_Mach_Effect_Thrusters.pdf
Was that discussed at the workshop?
Correct.
In the ship's frame, the only one which matters, the energy needed to alter velocity in relation to some desired destination is always the same as the ship's mass does not alter. Well not so much as it matters.
BTW Jim Woodward makes a good comment:
http://ssi.org/epi/Over-Unity_Argument_&_Mach_Effect_Thrusters.pdfQuoteWe routinely hear a criticism of METs based upon an argument that claims: if a
MET is operated at constant power input for a sufficiently long time, it will acquire
enough kinetic energy to exceed the total input energy of operation. Assuming this
argument to be correct, critcs assert that METs violate energy conservation as the ratio of
the acquired kinetic energy to total input energy exceeds “unity.”
Contrary to this “over-unity” assumption, this argument is based on flawed
physics and, consequently, wrong. The fact that the argument applies to all simple
mechanical systems (in addition to METs) should have alerted critics to their mistake.
But it didn’t.
So, a dumb idea that should have been quickly buried is still with us. The
purpose of this essay is to carry out a long overdue burial.
Interesting paper. I glanced at it and found the math was within my ability. So I printed it out to take a closer look. I think I will be able to find something wrong in his argument. But I may not be able to. Whatever the result is, I will write a swift report about my findings.
As promised, I wrote a short report. The attached picture is a screen short of the first page of the report. The whole report is also attached to this email. As meberbs, I now think Professor Woodward does not have credit in his theory.
These thrusters require "damping" to operate. If there is no damping, there is no thrust. Damping is a resistive loss of power. So if energy is put into it, and energy is lost to generate thrust, then there is no way it can be an over-unity device. -
#1037 by meberbs on 27 Sep, 2016 03:58
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The power expended x time in the ship frame is not really jumping frames, but I get why you think it is.
It's not wrong to compare but to equate. Some are saying power expended x time in the ships frame must equal or exceed the total kinetic energy in the earth observer frame where the ship starts from rest. And if the velocity exceeds a critical number, the acceleration just falls off to conserve energy. I used to think that but now I don't. What magic mechanism alerts the ship that it's crossed that number wrt earth frame and decreases the acceleration?
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What we are calculating is how much energy is in the big battery attached to the drive in the initial rest frame before it starts accelerating. When the battery is drained in the final moving ship frame (assume to 0), the battery also will have 0 potential energy as determined in the initial rest frame. (At relativistic velocities, there are some caveats, since the field of a moving point charge is not uniform in all directions, but for the example Gilbertdrive was looking at this would be a factor of 3*, when the failure of CoE is a factor on the order of 10000000.)
The next question about the magic mechanism is one you would have to ask one of the people who support a theory like Shawyer's. Theories like the Mach effect, degradable QV, etc. provide effective propellant interactions, or preferred frames that allow CoE to be conserved. Not being able to explain how the theory matches with CoE is one of the many problems with Shawyer's theory.
*the relativistic effect on potential energy is non-trivial, energy stored in the fields, radiation reaction, etc. has to be considered, and the field dependence with angle relative to motion means that 2 equal charges a fixed distance apart could have different stored energy depending on their angle relative to the direction of motion, but length contraction probably cancels this. I may work out the details for myself if I have time, but at most it should just be a factor of 1/sqrt(1-v^2 / c^2). -
#1038 by as58 on 27 Sep, 2016 04:00
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It is an authority argument. "If it is published, there is no big mistake"
At least, you should concede that the reviewer who accepted the Kinetic Energy to be calculated by 1/2*mv² for a speed of 0,67C made here a mistake, since the relativist formula was needed. The aim was to calculate a ratio that is around 0,31. so the relativist formula was making a real difference.
Also, the main point of my intervention was to show that in Shawyer theory paper, the thrust is supposed to decrease as acceleration from the time frame of the departure of the ship was increasing, so that CoE is verified. Are you convinced by the extracts that I have given, or do you think that, is this paper theory, the force is supposed to be constant ?
Here, the question is not what is true, it is what Shawyer is saying. Once we will agree on what Shawyer is saying in his theory paper, we can go to the other debate.
I have no idea how Shawyer's 2015 Acta Astronautica paper has passed review.
(To read the formulas below you'll have invoke your built-in latex interpreter...)
The efficiency calculation (Eqs. 9-13) is completely pointless and the efficiency as defined in Eq. 13 is always 1. Basically (for the sake of simplicity in a non-relativistic case) Eq. (9) is the well known formula P=Tv, where P is power, T is thrust (force) and v is the spacecraft velocity (and we'll use a reference frame where the spacecraft starts at rest, so v(0)=0). Then energy used for accelerating the spacecraft by time t_a is E_in(t_a)=\int_0^t_a P(t) dt = \int_0^t_a T(t)v(t) dt. Inserting T=ma (m is spacecraft mass, a is its acceleration) we get E_in(t_a)=\int_0^t_a ma(t)v(t) dt = m\int_0^t_a d/dt[v(t)] v(t) dt = m/2 \int_0^t_a d/dt[v(t)^2] dt = (m/2)v(t_a)^2=E_k. Shawyer's Eq. 10 for E_in expresses this using the 'average' velocity, which he never seems to define. In case of time-varying thrust T in Eq. 10 should also be some sort of average, but in the paper it seems that T is assumed constant, which means that v_{av} = v(t_a)/2 (Shawyer uses V_T for v(t_a). You can check that in that case Eq. 13 yields 1 after you use v(t_a)=a t_a=T/m t_a and plug in the expression for thrust from Eq. 8 ).
So, shockingly, classical mechanics seems to be consistent: if an object is accelerated with a given power, at the end its kinetic energy is the same as energy used for accelerating the object. However, in Shawyer's theory 'mechanical power' P_{mech} comes from electrical (microwave) power P_0 through mystically energy multiplying resonating cavity, as shown in Eq. 8. To really calculate the efficiency one should use E_{in}=t_a P_0 (possibly with some correction for efficiency in converting to microwave power). With high enough Q, it's easy to get over-unity efficiency.
The reason Shawyer gets e_{to}=0.363 instead of 1 for his 'spaceplane' seems to be that numbers in Table 4 are not consistent. If you plug numbers in the Table to his formulas, acceleration becomes about 16.5 m s^-2 and the final velocity after 1300 seconds about 21.5 km/s. His 7.8 km/s apparently comes from the text, where he discusses the mission profile with acceleration 6 m s^-2; however, that acceleration is not consistent with the parameters in the table.
There's of course the caveat that I may have misunderstood Shawyer's paper completely. That is possible because the paper is very confusingly written and full of errors (typos in equations, undefined symbols etc.). -
#1039 by meberbs on 27 Sep, 2016 04:39
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As promised, I wrote a short report. The attached picture is a screen short of the first page of the report. The whole report is also attached to this email. As meberbs, I now think Professor Woodward does not have credit in his theory.
That was a nice report.
Just to clarify one point, the Mach effect has been explained in other places in a way where the device can exchange momentum and energy with distant objects. The figure of merit equation would not necessarily apply.
This is not a disproof of the emDrive or Mach effect, just a conclusion that Woodward's paper is wrong, and propellantless thrusters that claim a constant Force/Power ratio greater than 1/c break CoE.
Happy "retirement" Paul!
